Green chromis school all died suddenly at same time

[wizzbane15]

I just had a school of 7 small green chromis, and a lone firefish, all die suddenly this morning. The lights turned on at 7, I fed the tank at 7:45, and by 8:30 all 7 chromis and the firefish were laying on bottom of tank with there mouths and a few of them even had their gills opened up wide.

Funny thing is that there are plenty of other fish and inverts in my tank that I would think are substantially more picky to changes in any tank parameters. My 125 DT has 2 yellow tangs, 1 atlantic blue tang, a bicolor and majestic angel, a few clowns, 2 coral banded shrimp, 1 cleaner shrimp, and a few pistol shrimp.

I run a SRO-2000 so I doubt I have an oxygenation problem through a custom sump that has a macro area where I have 6 mangroves growing and a separate deep mud section

Water paramters are as follows (also, my system is RKE controlled):

PH- 8.6 (reading was high becauseI was coming off my nightly kalk dose over an 8 hour period)
Nitrate- 0
Calcium- 550 (reading was high because I was coming off my nightly kalk dose over an 8 hour period
salinity - 1.225
ORP- 320ish (this is lower than I usually see as it normally is in the 400's).

I will try to upload some pictures of the fish.

[ShannyG]

Caveat: I know nothing. But I would be inclined to blame the kalk dose.

[slief]

Did your ORP drop around the same time the fish died? If so, I'd be looking at something related to your water quality. While 300 ORP isn't necessarily low by any means, a sudden drop of ORP is an indication of something going on. It could be o2 related but that's unlikely. If it were o2 related, I'd expect to see the larger fish poking their mouths out of the top of the water gasping for air. Kalk could be something to look at but a kalk overdose usually results in cloudiness. I'd run ammonia and nitrate tests just to see if there are any spikes there as well. Something is likely going on with your chemistry. The only other thing I can think of would be something like an anemone, sea hare, sea apple or box fish dying.

[rwb500]

550 Ca is way too high, with or without recent kalk dose. there's no way your calcium went from a proper level to 550 with one day's worth of kalkwasser.

[pyithar]

not being a tang police but you've got plenty of fish for a 125G imo. i think you made a typo on your salinity. all the fish would be dead by now with a 1.225 salinity.

[araspor]

I once had 3 disappear at the same time. They didn't jump, not in the sump. I really have no idea where they went.

[wizzbane15]

I found the culprit (I think). I had a green bubble tip anemone that died behind a rock pile. I saw the stringy parts of it this morning and pulled out the mess of goo. I am going to chalk this one up to the anemone ans everything else seemed /seems fine.

[slief]

Originally Posted by wizzbane15

I found the culprit (I think). I had a green bubble tip anemone that died behind a rock pile. I saw the stringy parts of it this morning and pulled out the mess of goo. I am going to chalk this one up to the anemone ans everything else seemed /seems fine.

That makes sense. That was pretty much what I expected. Anemones dying will do it as I mentioned in my previous post. Glad you got to the bottom of the mystery. Hopefully you were able to vacuum the rest out and do some water changes.